AIR iOS hard crashes: wakeup - Observed 503/sec over 300 secs

Question

Hi,
for a project I had to download a file with around 3GB.
So I decided to write a chunk based download controller, which easily does the following:
- open an URLStream
- Load the file by URLRequest
- Wait for the progress events and check, that we have more than 5MB in the buffer
- Write the bytes to an local file by using an Bytearray+Filestream combination
Additional I have implemented a workaround for the file size limit regarding to the Android specs,
that the local files is chunked when, the file exceeds the file size limit.
This solution works fine in this cases / test systems:
- Desktop - Windows
- Desktop - Mac
- Android - Debug
- Android - Release
- iOS 8.1.3 - Debug - fast interpreter mode
But when I try to compile and run / debug the app for iOS with the following modes:
- Release build Store
- Release build AdHoc
- Debug build without fast interpreter
The app crashes hard during the download.
I isolated my download controller and created a simple test app, which is using a simple sprite
and runs the download controller.
During the download the app is not completely hard crashing but the xcode console detects 1-2 crashes:
Feb 25 09:57:29 iPad-mini ReportCrash[422] <Error>: task_set_exception_ports(B07, 400, D03, 0, 0) failed with error (4: (os/kern) invalid argument)
Feb 25 09:57:29 iPad-mini ReportCrash[422] <Notice>: ReportCrash acting against PID 421
Feb 25 09:57:29 iPad-mini ReportCrash[422] <Notice>: Formulating crash report for process DownloadAndTarUnitTester[421]
Feb 25 09:57:30 iPad-mini ReportCrash[422] <Notice>: Saved report to /var/mobile/Library/Logs/CrashReporter/ExcResource_DownloadAndTarUnitTester_2015-02-25-09 5729_iPad-mini.ips
Relating crash report:
Incident Identifier: 868898CC-9DAF-422E-889C-F397C2595E8F
CrashReporter Key:   eb14103bfc730ebe68f5b1970597c35e3006eb42
Hardware Model:      iPad2,5
Process:             DownloadAndTarUnitTester [421]
Path:                /private/var/mobile/Containers/Bundle/Application/7F892804-5378-4B81-BE54-C1EDA66FCF96/Do wnloadAndTarUnitTester.app/DownloadAndTarUnitTester
Identifier:          DownloadAndTarUnitTester
Version:             0.0.0 (0.0.0)
Code Type:           ARM (Native)
Parent Process:      launchd [1]
Date/Time:           2015-02-25 09:57:29.864 +0100
Launch Time:         2015-02-25 09:56:48.087 +0100
OS Version:          iOS 8.1.3 (12B466)
Report Version:      105
Exception Type:  EXC_RESOURCE
Exception Subtype: WAKEUPS
Exception Message: (Limit 150/sec) Observed 1079/sec over 300 secs
Triggered by Thread:  0
Thread 0 name:  Dispatch queue: com.apple.main-thread
Thread 0 Attributed:
0   libsystem_pthread.dylib       0x3a1a2eba 0x3a1a2000 + 3770
1   CoreFoundation                 0x2befeb68 0x2be32000 + 838504
2   CoreFoundation                 0x2be4bb2c CFRunLoopRunSpecific + 472
3   CoreFoundation                 0x2be4b93e CFRunLoopRunInMode + 102
4   GraphicsServices               0x3320004c 0x331f7000 + 36940
5   UIKit                         0x2f43df1c 0x2f3d0000 + 450332
6   DownloadAndTarUnitTester       0x0026761c 0x57000 + 2164252
7   DownloadAndTarUnitTester       0x006ca730 0x57000 + 6764336
Thread 1 name:  Dispatch queue: com.apple.libdispatch-manager
Thread 1:
0   libsystem_kernel.dylib         0x3a1122c8 kevent64 + 24
1   libdispatch.dylib             0x3a034e44 _dispatch_mgr_invoke + 276
2   libdispatch.dylib             0x3a034b76 _dispatch_mgr_thread$VARIANT$mp + 34
Thread 2 name:  BackgroundThread
Thread 2:
0   libsystem_kernel.dylib         0x3a125b38 __psynch_cvwait + 24
1   libsystem_pthread.dylib       0x3a1a43dc _pthread_cond_wait + 516
2   libsystem_pthread.dylib       0x3a1a52ac pthread_cond_wait + 36
3   DownloadAndTarUnitTester       0x0041dd90 0x57000 + 3960208
4   DownloadAndTarUnitTester       0x002fbe78 0x57000 + 2772600
5   DownloadAndTarUnitTester       0x0041db60 0x57000 + 3959648
6   DownloadAndTarUnitTester       0x0041dbb4 0x57000 + 3959732
7   DownloadAndTarUnitTester       0x0041d8d4 0x57000 + 3958996
8   libsystem_pthread.dylib       0x3a1a4e64 _pthread_body + 136
9   libsystem_pthread.dylib       0x3a1a4dd6 _pthread_start + 114
10  libsystem_pthread.dylib       0x3a1a2b80 thread_start + 4
Thread 3 name:  BackgroundThread
Thread 3:
0   libsystem_kernel.dylib         0x3a125b38 __psynch_cvwait + 24
1   libsystem_pthread.dylib       0x3a1a43dc _pthread_cond_wait + 516
2   libsystem_pthread.dylib       0x3a1a52ac pthread_cond_wait + 36
3   DownloadAndTarUnitTester       0x0041dd90 0x57000 + 3960208
4   DownloadAndTarUnitTester       0x002fbe78 0x57000 + 2772600
5   DownloadAndTarUnitTester       0x0041db60 0x57000 + 3959648
6   DownloadAndTarUnitTester       0x0041dbb4 0x57000 + 3959732
7   DownloadAndTarUnitTester       0x0041d8d4 0x57000 + 3958996
8   libsystem_pthread.dylib       0x3a1a4e64 _pthread_body + 136
9   libsystem_pthread.dylib       0x3a1a4dd6 _pthread_start + 114
10  libsystem_pthread.dylib       0x3a1a2b80 thread_start + 4
Thread 4:
0   libsystem_kernel.dylib         0x3a12619c __semwait_signal + 24
1   libsystem_c.dylib             0x3a085de0 nanosleep + 168
2   DownloadAndTarUnitTester       0x0041d93c 0x57000 + 3959100
3   DownloadAndTarUnitTester       0x0028578c 0x57000 + 2287500
4   DownloadAndTarUnitTester       0x0028574c 0x57000 + 2287436
5   DownloadAndTarUnitTester       0x0041db60 0x57000 + 3959648
6   DownloadAndTarUnitTester       0x0041dbb4 0x57000 + 3959732
7   DownloadAndTarUnitTester       0x0041d8d4 0x57000 + 3958996
8   libsystem_pthread.dylib       0x3a1a4e64 _pthread_body + 136
9   libsystem_pthread.dylib       0x3a1a4dd6 _pthread_start + 114
10  libsystem_pthread.dylib       0x3a1a2b80 thread_start + 4
Feb 25 09:59:54 iPad-mini ReportCrash[440] <Error>: task_set_exception_ports(B07, 400, D03, 0, 0) failed with error (4: (os/kern) invalid argument)
Feb 25 09:59:54 iPad-mini ReportCrash[440] <Notice>: ReportCrash acting against PID 436
Feb 25 09:59:54 iPad-mini ReportCrash[440] <Notice>: Formulating crash report for process DownloadAndTarUnitTester[436]
Feb 25 09:59:55 iPad-mini ReportCrash[440] <Notice>: Saved report to /var/mobile/Library/Logs/CrashReporter/ExcResource_DownloadAndTarUnitTester_2015-02-25-09 5954_iPad-mini.ips
Relating crash report:
CrashReporter Key:   eb14103bfc730ebe68f5b1970597c35e3006eb42
Hardware Model:      iPad2,5
Process:             DownloadAndTarUnitTester [436]
Path:                /private/var/mobile/Containers/Bundle/Application/7A313D06-6D0C-4583-8CCA-C0994F6BCAB0/Do wnloadAndTarUnitTester.app/DownloadAndTarUnitTester
Identifier:          DownloadAndTarUnitTester
Version:             0.0.0 (0.0.0)
Code Type:           ARM (Native)
Parent Process:      launchd [1]
Date/Time:           2015-02-25 09:59:54.603 +0100
Launch Time:         2015-02-25 09:58:25.203 +0100
OS Version:          iOS 8.1.3 (12B466)
Report Version:      105
Exception Type:  EXC_RESOURCE
Exception Subtype: WAKEUPS
Exception Message: (Limit 150/sec) Observed 503/sec over 300 secs
Triggered by Thread:  12
Thread 0 name:  Dispatch queue: com.apple.main-thread
Thread 0:
0   libsystem_kernel.dylib         0x3a112518 mach_msg_trap + 20
1   libsystem_kernel.dylib         0x3a11230c mach_msg + 36
2   CoreFoundation                 0x2bf00596 __CFRunLoopServiceMachPort + 142
3   CoreFoundation                 0x2befeb5c __CFRunLoopRun + 1012
4   CoreFoundation                 0x2be4bb2c CFRunLoopRunSpecific + 472
5   CoreFoundation                 0x2be4b93e CFRunLoopRunInMode + 102
6   GraphicsServices               0x3320004c GSEventRunModal + 132
7   UIKit                         0x2f43df1c UIApplicationMain + 1436
8   DownloadAndTarUnitTester       0x002da61c 0xca000 + 2164252
9   DownloadAndTarUnitTester       0x0073d730 0xca000 + 6764336
Thread 1 name:  Dispatch queue: com.apple.libdispatch-manager
Thread 1:
0   libsystem_kernel.dylib         0x3a1122c8 kevent64 + 24
1   libdispatch.dylib             0x3a034e44 _dispatch_mgr_invoke + 276
2   libdispatch.dylib             0x3a034b76 _dispatch_mgr_thread$VARIANT$mp + 34
Thread 2:
0   libsystem_kernel.dylib         0x3a1269cc __workq_kernreturn + 8
1   libsystem_pthread.dylib       0x3a1a2e9c _pthread_wqthread + 788
2   libsystem_pthread.dylib       0x3a1a2b74 start_wqthread + 4
The debugger did not detect any error.
I tested AIR 15, 16.
Maybe this is a iOS restriction regarding to the new battery consumption limitations for apps.
So I tried to:
- Set the framerate to max. 30FPS
- Extend to buffer size before write to test on ProgressEvent form 512KB to 5MB
But the crashes are staying and the observed wakeups are not reducing.
Has anyone an idea how to solve this?

Answer 1

Thanks for the reply. I'm not sure if it's iOS 8 only, and I'm having a hard time reproducing the crash at my office after letting it run for 24 hours. I only see the crash results on the iPad after the fact.
I can send the code for the project to someone, if that will help. Who would I send it to?
In the meantime, do you have any recommendations for how to force an excess number of wakeups? I figure if I can force the crash, then I can see if it helps to try the latest AIR SDK or make other changes.
Also, here is a little more info about the project:
- Uses Starling.
- Uses video playing in a webview (with darkredz ANE).
- Uses Apple's Guided Access to lock out app switching.
Do any of these things seem more likely to cause issues with thread management? I'm guessing that the app never goes into background mode, since it's locked to this one app. But would the iPad going to sleep force it into background mode somehow?
Thanks for the help.
John